BIRTH STATISTICS Birth records are secured by registration in those civil divi sions that secure sufficiently complete records to be of value. Legal responsibility is placed upon physicians and mid-wives to make reasonably prompt returns in accordance with prescribed rules and upon special foiius (Fig. 127), to designated officials. The securing of reasonably complete birth records is a difficult matter and at least in the United States is probably nowhere mo per cent. complete.
Birth records are of value to individuals whose births are recorded from the standpoints of giving legal proof of citizen ship, age and parentage, all of which are sometimes necessary to secure passports, residence, to secure employment, to prove legitimacy, to inherit property and in numerous other ways to enable an individual to enjoy the rights of citizenship. From a public health standpoint birth registration is of importance as it enables health authorities to intelligently combat infant mortality by means we have already considered.
All children who breathe after birth should be registered as births, while still births should not be recorded in either the groups of births or deaths, but placed in an independent group.
A rough check on the completeness of registration may be secured by comparing the total number of births registered by the number of children under 1 year of age enumerated in any census year.
The births in a given population may be expressed for com parative purposes in the following ways: (a) The rate or number per moo of the entire population.
(b) The rate per moo women of child bearing age (c) The legitimate birth rate per moo married women of 15-45.
(d) The illegitimate birth rate per moo unmarried women of 15-45.
The first of these methods of expression is known as the crude birth rate, and is subject to the same objections when employed for comparative purposes that are raised to the crude death rate. These will be considered later. These rates are puted in the same manner as the death rates, as shown later.
The second method of expression gives a better idea of the fecundity of a population, while the third and fourth methods when used together give a still better idea. These should be employed when it is desired to compare the births in one com munity with those of another.
The frequency of births varies widely with different races and nationalities, in different parts of a country, state or even a city. The crude rate may vary in the extreme from as to 39 per thousand. The following factors influence the birth rate: (a) the age distribution of the population; (b) the propor tion of the two sexes; (c) the number of first marriages; (d) the age at marriage; (e) the economic condition of the country, and (f) social and hygienic conditions.